1. Field
The invention relates to a torsional restraint for restraining a jet pump assembly.
2. Description of the Related Art
Conventional boiling water reactors include a reactor pressure vessel (RPV) which surrounds a core shroud. The core shroud, in turn, surrounds the reactor core. Generally, each of the core shroud and the reactor pressure vessel are cylindrically shaped such that an outer diameter of the core shroud is less than an inner diameter of the reactor pressure vessel. Between the reactor pressure vessel wall and the core shroud wall is an annular space in which jet pump assemblies are typically located.
FIG. 1 illustrates a conventional jet pump assembly 25 located in the aforementioned annulus. As illustrated in FIG. 1, an inlet nozzle 10 extending through a sidewall 15 of the RPV 20, is coupled to the jet jump assembly 25. The jet pump assembly 25 includes a riser pipe 30 that extends between the shroud 35 and the sidewall 15 of the RPV 20. The riser pipe 30 is coupled to two jet pumps 35A and 35B by a transition assembly 40. Each jet pump 35A and 35B includes a jet pump nozzle 42, a suction inlet 45, an inlet mixer, and a diffuser 55. For example, the first jet pump 35A includes a first inlet mixer 50A and the second jet pump 35B includes second inlet mixer 50B. The jet pump nozzles 42 are positioned in the suction inlets 45 that are located at a first end of inlet mixers 50A and 50B. The diffusers 55, are coupled to a second end of inlet mixers 50A and 50B by a slip joint 65. Typically, both of the inlet mixers 50A and 50B and the diffusers 55 are formed of multiple cylindrical sections. Circumferential welds 70 join the cylindrical sections together.
A support member 75 typically surrounds the riser pipe 30 and connects to the riser pipe 30 via a weld 80 which may span approximately 180 degrees around the circumference of the riser pipe 30. The inlet mixers 50A and 50B are secured to the riser pipe 30 via a restrainer bracket 100.
Referring to FIG. 2, the conventional restrainer bracket 100 includes a first yolk-like member 105A and a second yolk-like member 105B surrounding the inlet mixers 50A and 50B. The conventional restrainer bracket 100 also includes at least two set screws 110 penetrating the yolk-like members 105A and 105B and pressing against the inlet mixers 50A and 50B. Main wedges 115 also are typically provided in gaps between the yolk-like members 105A and 105B and the inlet mixers 50A and 50B so that the restrainer bracket 100 securely retains the inlet mixers 50A and 50B between the set screws 110 and the main wedges 115.